We measured dissolved organic carbon (DOC), δ¹³C-DOC, fluorescent dissolved organic matter (FDOM), dissolved inorganic and organic nitrogen (DIN; DON), dissolved inorganic phosphate (DIP), and radium isotopes (²²³Ra, ²²⁴Ra, and ²²⁶Ra) in three different bays: Gwangyang Bay (GB), Suyoung Bay (SB), and Ulsan Bay (UB), Korea. The water residence times based on Ra isotopes were approximately 15 (±7) for GB and 1–3 days for SB and UB. UB and SB showed clear two (terrestrial and marine) endmember mixing trends for DOC, DIN, and DIP. In addition, significant “excess” DOC (10–50% of outer bay) was observed for SB under depleted nutrient conditions. GB, which had the longest water-residence time, showed depleted DIN and DIP, with large “excess” DOC (40–60% of the outer bay) and DON (10–40% of the outer bay) concentrations. The excess DOC observed in SB and GB was found to be marine in origin, although there was a slight influence of terrestrial DOC in the low-salinity waters of SB based on δ¹³C-DOC values. Terrestrial humic-like FDOM was conservatively mixed in the three bays. The net fluxes of these components, estimated using the water residence times, suggest that GB is a significant source of DOM (DOC, DON, and humic FDOM) but a sink of DIN and DIP. SB and UB are the sources of inorganic nutrients as well as DOM to the open ocean. Therefore, our study reveals that the residence time of coastal embayment play an important role in the biogeochemical production and alteration of nutrients and DOM.

我们测量溶解的有机碳（DOC），δ ¹³ C-DOC，荧光溶解的有机物质（FDOM），溶解的无机和有机氮（DIN; DON），溶解的无机磷酸盐（DIP）和镭同位素（²²³镭，²²⁴太阳神和²²⁶Ra）位于三个不同的海湾：韩国的光阳湾（GB），水荣湾（SB）和蔚山湾（UB）。基于Ra同位素的水停留时间，GB约为15（±7），SB和UB约为1-3天。UB和SB显示了DOC，DIN和DIP的两个明显的（地面和海洋）端成员混合趋势。此外，在营养缺乏的情况下，SB的DOC含量显着“过量”（外湾的10％至5​​0％）。保水时间最长的GB显示耗尽的DIN和DIP，其中有大量的“过量” DOC（外湾的40-60％）和DON（外湾的10-40％）。在SB和GB观察到的过量DOC被认为是起源于海洋，虽然有在SB的低盐度水基于δ陆地DOC的轻微影响¹³C-DOC值。在三个海湾中，保守地混有类似陆地腐殖质的FDOM。使用水停留时间估算的这些成分的净通量表明，GB是DOM的重要来源（DOC，DON和腐殖质FDOM），但是DIN和DIP的汇。SB和UB是无机养分的来源，也是通向大洋的DOM的来源。因此，我们的研究表明，海岸带的滞留时间在生物地球化学生产以及养分和DOM的改变中起着重要作用。